This invention relates to deformable lenses, particularly for use in eyeglasses for older people.
About the age of 40, many individuals, who had perfect vision at all distances, find that their near vision is fading and their distant vision is also showing signs of weakness. The reason is not usually illness or accident. About the age of 40, the lens of the eye, which adjusted its form naturally, dependent upon the distance of the object being viewed from the viewer and the size of his or her pupil, has doubled in size and increased its density about five times since birth. In other words, most peoples' lenses no longer have the flexibility or maneuverability that they had in their younger years.
Benjamin Franklin initially prescribed bifocals for this problem. Trifocals were later added. Recently, blended bifocals have been developed. This type of lens has the power difference, usually an increased power of 2.50 diopters blended so that there are no lines and the power changes gradually. By tipping the head, wearers can choose which lens or power they want to use.
The problems that exist with these solutions include poor vision walking down steps (the power in the lower portion of the glasses is for 16 inches); reading at a desk (the width of the bifocal in the blended bifocal is narrow in width and the reader has to turn his or her head to read instead of just using the eyes); and the power of the reading glasses one may be wearing may not be strong enough for the task at hand, i.e., much greater magnification is necessary resulting in the individual substituting a stronger pair of glasses.
It is recognized in the medical community that near-sighted or far-sighted persons who wear bifocals have approximately three feet of uncorrected space between the power correction of the near lens and the correction of the far lens. This uncorrected space results in blurry vision for such wearers of bifocals. Responding to this problem, wearers usually attempt to displace bifocals fore and aft in front of their faces. Usually such displacement covers approximately a distance between a quarter inch and a maximum of approximately one inch before wearers feel comfortable. In response to this problem, quite a few attempts dealing with adjustable frames for a pair of eyeglasses have been made.
Thus, U.S. Pat. No. 5,162,824 to Klemka discloses an adjustable lens spectacle including a rigid front frame and a slidable rear frame mounted parallel thereto. The rear frame is provided with a drive motor contained within a respective temple leg, and a drive means coupling the motor with the rear frame for effecting reciprocation of the rear frame relative to front frame. The frame is further provided with a reversing switch mounted outside the frame. A distance at which the rear frame travels is grossly inadequate to compensate for the uncorrected space mentioned above. Further, a cross plate serving as a guide for the rear frame is esthetically unappealing because the displaceable frame cannot fit the front frame, thereby increasing the overall size of the disclosed pair of eyeglasses. Typically, a wearer of the assemble pair of eyeglasses would experience considerable inconvenience because the overall structure is neither compact nor light.
Another known device for aiding vision of images, primarily for magnifying a television picture, includes a pair of spectacles, comprising eye-piece lenses mounted in a frame, and binocular objective lenses disposed in front of each eye-piece lens and supported by an extension to the frame of spectacles. The device further has a means for displacing objective lenses along the optical axis.
U.S. Pat. No. 3,659,931 discloses an eyeglass frame having a manually adjustable means for individually moving each lens toward and away from the wearer's eye to vary the lens-eye separation for optimum focus.
In a recent patent, U.S. Pat. No. 6,076,927, Owens has provided a pair of eyeglasses adapted to vary a focal length between the lens of the glasses and the wearer's eyes to compensate for uncorrected space that occurs for near sighted persons wearing bifocals. According to Owens' invention, the lenses are movably mounted upon a frame which is stationary on the wearer's faces. Located on each temple piece of the frame is an actuator adapted to displace the eyepieces up to one inch from the wearer's eyes.